OCT 2013

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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October 2013 EW RETINA 107 Studies highlight risk gene for AMD T hree studies based on research funded by the National Institutes of Health (NIH) identify the same risk gene for age-related macular degeneration (AMD), according to a news brief from the National Eye Institute (NEI). The studies were reported in Nature Genetics. AMD is a common cause of vision loss in older people, and the cause of it is not entirely understood, with different age, hereditary, and lifestyle factors playing a role. The information in the studies highlights the link between AMD and the genes encoding the complement system, which is a set of proteins that has an important role in immune responses and inflammation. The C3 gene is particularly mentioned in this correlation. According to the news brief, studies of genetics have noted the role of the complement system in AMD. These three new studies provide further information and insights. The complement system is made up of many proteins working together, and in addition to inflammatory and immune responses, it also helps with the function of the retina. There are nine complement component proteins. Additionally, by Ellen Stodola EyeWorld Staff Writer there are CFH and CFI genes associated with the complement system that help inhibit it from attacking the cells of the body. These new studies focused on the association between AMD and rare gene variants in an attempt to find more information about the disease. It is believed that these rare variants would have more of an impact on the function of the genes and the likelihood of AMD. The studies also looked at information on the link between AMD Effect of vision loss on travel patterns by Ellen Stodola EyeWorld Staff Writer A recent study investigated decreased visual acuity (VA) from age-related macular degeneration (AMD) and visual field (VF) loss from glaucoma and how these factors may impact patients' travel patterns. "Alteration of Travel Patterns With Vision Loss from Glaucoma and Macular Degeneration" was published online in the September 12 edition of JAMA Ophthalmology. A cross-sectional study was conducted with the idea of determining whether the two factors did indeed restrict travel patterns for these patients. Participants for the study were recruited from an eye clinic, and to determine their travel patterns, cellular tracking devices were used to record their real-world routines. The study consisted of 61 control subjects who had normal vision, 84 subjects with glaucoma with bilateral VF loss, and 65 subjects with AMD with bilateral or severe unilateral loss of VA. The participants had their location tracked every 15 minutes between 7 a.m. and 11 p.m. for seven days. Additionally, the average daily excursion size and average daily excursion span were defined for each participant in the study. According to the results, "In multivariable models comparing subjects with AMD and control subjects, average excursion size and span decreased by approximately one-quarter mile for each line of better-eye VA loss (P≤.03 for both)." The results were similar when comparing those with VF loss from glaucoma with the control group, however, these results were not considered statistically significant. "Being married or living with someone and younger age were associated with more distant travel, while less-distant travel was noted for older individuals, African Americans, and those living in more densely populated regions," the abstract said. Based on the results, it was determined that AMD-related loss of VA is associated with restriction of travel to more nearby locations, but glaucoma-related loss of VF is not. EW and heritability. "The common gene variants that have been linked to AMD only explain about half its heritability," said Johanna M. Seddon, MD, professor of ophthalmology and director of the ophthalmic epidemiology and genetics service, Tufts Medical Center, Boston. "Rare variants can help fill in that gap and may point to new therapies." All of the studies highlighted a single rare variant in the C3 gene that increases the risk of AMD. EW References 1. Zhan X, Larson DE, Wang C, et al. Identification of a rare coding variant in complement 3 associated with age-related macular degeneration. Nature Genetics, September 2013. DOI: 10.1038/ng.2758. 2. Seddon JM et al. Rare variants in CFI, C3 and C9 are associated with high risk of advanced age-related macular degeneration. Nature Genetics, September 2013. DOI: 10.1038/ng.2741. 3. Helgason H et al. A rare nonsynonymous sequence variant in C3 is associated with high risk of age-related macular degeneration. Nature Genetics, September 2013. DOI: 10.1038/ng.2740. Editors' note: Research for these studies was funded partly by the NEI and NEI grants, as well as the NIH's Human Genome Research Institute.

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